The plastic deformation of polycrystalline aggregates

Abstract

For a number of metallic polycrystalline aggregates, it is shown experimentally that [sgrave]_f, the flow stress at constant strain, is related to the grain diameter l by where [sgrave]₀ and k are constants. This has the same form as the relationship between the lower yield point, when this occurs, and grain size. An explanation is given by an extension of Taylor's theory to allow for the resistance at the grain boundary to the formation of a slip band. Dislocation-locking and a small number of slip systems are shown to favour a strong grain-size dependence of [sgrave]_f and this explains the variation of this dependence amongst the common metals and alloys.